G 1

vers ted d G vior ed nd h th cles we hni ve gain s (Row d have g the u d perfo e geom brane (Thiel et al., 2006; Bostwick et al., 2007, 2008; Rowe et al., 2009) have demonstrated that shrinkage of up to 23 % could be induced in the laboratory by the application of cyclic wetting and drying. The A novel field approach to addressing the concern regarding separation of panels of GCL3 and GCL4 when used as part of a composite liner for a large (60 ha) heap leach pad at the Carlota Mine in Arizona, USA (latitude 33N) was recently proposed by Thiel and Thiel (2009). The composite liner was constructed on a subgrade of a gravelly, silty sand of low plasticity that is subject to rapid drying in the local climate. The as-compacted subgrade moisture content was 10–12 % but due to the arid climate the moisture content decreased with depth. Depending on th